JP2009139510A - Method for manufacturing polarizing plate, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing plate for improving adhesion between a polarizer and a transparent protective film and preventing the occurrence of knicks on a boundary face of the polarizer and the transparent protective film. <P>SOLUTION: This method of manufacturing the polarizing plate 10 includes steps of: applying surface reforming treatment and alkaline treatment on a surface of the transparent protective film 12: and bonding the surface of the transparent protective film 12 subjected to the surface reforming treatment and the alkaline treatment and the polarizer 11 through polyvinyl alcohol adhesive containing metallic compound colloid. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polarizing plate manufacturing method, a polarizing plate obtained by the manufacturing method, and a liquid crystal display device including the polarizing plate. In particular, the present invention can improve the adhesiveness between the polarizer and the transparent protective film, and can also prevent the occurrence of nicks at the interface between the polarizer and the transparent protective film, and the manufacturing method of the polarizing plate. The present invention relates to an obtained polarizing plate and a liquid crystal display device including the polarizing plate.

  In a liquid crystal display device, it is indispensable to dispose a polarizer on both sides of a glass substrate on which a liquid crystal panel surface is formed due to the image forming method. The polarizer is generally obtained by dyeing a polyvinyl alcohol film with a dichroic substance such as iodine, cross-linking with a cross-linking agent, and uniaxially stretching to form a film. Since this polarizer is produced by stretching, it easily contracts. In addition, since the polyvinyl alcohol film uses a hydrophilic polymer, it is very easily deformed particularly under humidified conditions. Moreover, since the mechanical strength of the film itself is weak, there is a problem that the film is torn. For this reason, the polarizing plate which supplemented intensity | strength is used by bonding together transparent protective films, such as a triacetyl cellulose, on both surfaces or one side of a polarizer. This polarizing plate is manufactured by bonding a polarizer and a transparent protective film through an adhesive.

  By the way, the use of liquid crystal display devices in recent years has been expanded and has been widely used from portable terminals to large-sized televisions for home use, and standards according to each application have been provided. In particular, since liquid crystal display devices for portable terminals are assumed to be carried around by users, the requirements for durability are very strict. For example, a polarizing plate is required to have durability that does not change its characteristics and shape even under humidified conditions that cause condensation.

  As described above, the polarizer is used as a polarizing plate whose strength is supplemented by a transparent protective film. As an adhesive for polarizing plates used for adhesion between a polarizer and a transparent protective film, a water-soluble adhesive is preferable. For example, a polyvinyl alcohol-based adhesive in which a crosslinking agent is mixed with a polyvinyl alcohol aqueous solution is used. However, when a polarizer and a transparent protective film are bonded together via a polyvinyl alcohol-based adhesive, peeling may occur at the interface between the polarizer and the transparent protective film under humidified conditions. This may be due to the fact that the polyvinyl alcohol resin, which is the main component of the polyvinyl alcohol adhesive, is a water-soluble polymer, so that the adhesive is dissolved under the dew condensation condition. For this problem, for example, an adhesive for polarizing plates containing a polyvinyl alcohol-based resin containing an acetoacetyl group and a crosslinking agent has been proposed (see Patent Document 1). However, the conventional technology as described in Patent Document 1 cannot sufficiently meet the strict demands on the durability of polarizing plates in recent years, and a polarizing plate that is more excellent due to the adhesion between the polarizer and the transparent protective film is desired. It has been.

On the other hand, when the polarizing plate is produced, there is a problem that a nick is generated when the polarizer and the transparent protective film are bonded together via the polyvinyl alcohol-based adhesive. This nick is a local unevenness defect generated at the interface between the polarizer and the transparent protective film. A knick is particularly likely to occur when a polyvinyl alcohol resin containing an acetoacetyl group is used as the polyvinyl alcohol adhesive. For this nick, for example, there is a method of obtaining a polarizing plate by using a polarizer obtained by treating the surface of a polyvinyl alcohol film with adjusted moisture content with a calender roll under predetermined conditions, and laminating it with a transparent protective film. It has been proposed (see Patent Document 2). However, in the conventional technology as described in Patent Document 2, it cannot be said that the occurrence of nicks can be sufficiently suppressed, and there is a demand for a polarizing plate in which the occurrence of nicks is further suppressed.
JP-A-7-198945 Japanese Patent Laid-Open No. 10-166519

  The present invention has been made in view of the above-described problems of the prior art, and can improve the adhesion between the polarizer and the transparent protective film, and also generate nicks at the interface between the polarizer and the transparent protective film. It is an object of the present invention to provide a method for producing a polarizing plate capable of inhibiting the above, a polarizing plate obtained by the production method, and a liquid crystal display device including the polarizing plate.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, the surface of the transparent protective film is subjected to surface modification treatment and alkali treatment, and a metal compound is bonded to the polarizer and the transparent protective film. It has been found that by using a polyvinyl alcohol-based adhesive containing a colloid, the adhesion between the polarizer and the transparent protective film can be improved, and the occurrence of nicks can be suppressed. Based on this new finding, the present inventors have completed the present invention.

  That is, the present invention includes a step of subjecting the surface of the transparent protective film to a surface modification treatment and an alkali treatment, and the surface modification treatment and the alkali treatment through a polyvinyl alcohol adhesive containing a metal compound colloid. And a step of bonding the surface of the transparent protective film and the polarizer together.

  As the surface modification treatment, it is preferable to apply at least one of corona discharge treatment, plasma treatment, and UV treatment in that continuous treatment is possible and economy and workability are excellent.

When a corona discharge treatment is applied as the surface modification treatment, a sufficient surface modification effect cannot be obtained if the discharge amount is less than 50 W · min / m ² , and sufficient adhesion between the polarizer and the transparent protective film is obtained. There is a possibility that it cannot be improved. On the other hand, if the discharge amount exceeds 150 W · min / m ² , the transparent protective film may be damaged.
Therefore, when corona discharge treatment is applied as the surface modification treatment, the discharge amount is preferably 50 to 150 W · min / m ² .

  The transparent protective film is formed of, for example, any polymer selected from polyvinyl alcohol polymers, norbornene polymers, acrylic polymers, and polyester polymers.

  An example of the metal compound colloid is alumina colloid.

  Moreover, this invention is provided also as a polarizing plate characterized by the above-mentioned manufacturing method.

  Furthermore, this invention is provided also as a liquid crystal display device provided with the said polarizing plate.

  According to the method for producing a polarizing plate of the present invention, it is possible to improve the adhesion between the polarizer and the transparent protective film, and to suppress the occurrence of nicks at the interface between the polarizer and the transparent protective film.

<A. Polarizing plate>
FIG. 1 is a longitudinal sectional view schematically showing a configuration of a polarizing plate according to one embodiment of the present invention. As shown in FIG. 1, a polarizing plate 10 according to the present invention includes a polarizer 11 and a transparent protective film 12 bonded to one side or both sides (both sides in the example shown in FIG. 1) of the polarizer 11.

<A-1. Polarizer>
The polarizer 11 is not particularly limited as long as it can convert natural light or polarized light into linearly polarized light, and a conventionally known one can be used. As the polarizer 11, a raw film made of a polymer film such as a polyvinyl alcohol film is dyed with a dichroic substance such as iodine or a dichroic dye, and is uniaxially stretched in the longitudinal direction (MD direction) of the film. Is common.

  The polymer film is not particularly limited, and various types can be used. Examples of the polymer film include polyvinyl alcohol films such as polyvinyl alcohol and partially formalized polyvinyl alcohol, polyethylene terephthalate films, ethylene / vinyl acetate copolymer films, and partially saponified films thereof. Further, cellulose-based films, polyene-oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products can also be exemplified. Among these polymer films, it is preferable to use a polyvinyl alcohol film since it is excellent in dyeability by a dichroic substance. The thickness of the polymer film is not particularly limited, but is preferably about 5 to 100 μm.

  The average degree of polymerization of the polymer that is the material of the polymer film is generally in the range of 500 to 10,000, preferably in the range of 1000 to 6000, and more preferably in the range of 1400 to 4000. When the polymer film is a polyvinyl alcohol film, the average saponification degree is preferably 75% mol or more, more preferably 98% mol or more, for example, from the viewpoint of solubility in water. More preferably, it is made into the range of 98.3-99.8 mol%.

  When the polymer film is a polyvinyl alcohol film, a film formed by any production method such as a casting method in which a stock solution dissolved in water or an organic solvent is cast, a casting method or an extrusion method is appropriately used. Can be used. A polyvinyl alcohol film having an in-plane retardation value of 5 to 100 nm is preferably used. Moreover, in order to obtain the polarizer 11 which has an in-plane uniform optical characteristic, it is preferable that the variation in the in-plane retardation value of a polyvinyl alcohol-type film is as small as possible. Specifically, the variation in the in-plane retardation value of the polyvinyl alcohol film as the raw film is preferably 10 nm or less, more preferably 5 nm or less, at a measurement wavelength of 1000 nm.

  As a manufacturing method of the polarizer 11, a dry stretching method or a wet stretching method is generally used. Although the manufacturing method of the polarizer 11 by the wet extending | stretching method is not specifically limited, For example, a swelling process, a dyeing | staining process, a bridge | crosslinking process, an extending | stretching process, washing with water to the said polymer film as a raw film A method of manufacturing by performing a series of manufacturing steps including a processing step and a drying processing step is common. In each of the above processing steps except the drying processing step, each processing is performed while immersing the film in a bath made of various solutions. The order, frequency, and presence / absence of swelling treatment, dyeing treatment, crosslinking treatment, stretching treatment, water washing treatment and drying treatment are not particularly limited, and several treatments may be performed simultaneously in one treatment step. Some processing may not be performed. For example, the stretching process may be performed after the dyeing process, or may be performed simultaneously with the swelling process or the dyeing process. A dyeing treatment may be performed after the stretching treatment. Moreover, it does not specifically limit as the extending | stretching processing method of the film to MD direction, For example, the method of extending | stretching by the peripheral speed difference between rolls is used. Moreover, you may add additives, such as a boric acid, a borax, and potassium iodide, suitably in the bath in which each process is performed. Therefore, the polarizer 11 contains boric acid, zinc sulfate, zinc chloride, potassium iodide, and the like as necessary. Further, in some of the above treatments, the film may be appropriately stretched in the MD direction or TD direction (width direction) by a conventionally known method, and may be subjected to a water washing treatment after each treatment.

  The thickness of the polarizer 11 is not particularly limited, but is preferably 5 μm to 40 μm. If the thickness is 5 μm or more, the mechanical strength will not be reduced, and if it is 40 μm or less, the optical characteristics will not be reduced, and thinning can be realized even when applied to a liquid crystal display device. Further, the transmittance (single transmittance) when measured with the polarizer 11 alone is preferably 43.0% or more, and more preferably in the range of 43.0 to 45.0%.

<A-2. Transparent protective film>
As the transparent protective film 12, if it is excellent in transparency, it will not specifically limit, A suitable thing can be used suitably. For example, the transparent protective film 12 is preferably formed from any one of a polyvinyl alcohol resin, a norbornene resin, an acrylic resin, and a polyester resin. Examples of the acrylic resin include polymethyl methacrylate, and examples of the polyester resin include polyethylene terephthalate and polyethylene naphthalate. The polyvinyl alcohol resin and norbornene resin will be described later. Although the thickness of the transparent protective film 12 is not specifically limited, Usually, it is about 20 micrometers-200 micrometers.

<A-2-1. Polyvinyl alcohol resin>
Polyvinyl alcohol resins include polyvinyl alcohol resins obtained by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, as well as unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonates, and the like. It is also possible to use a polyvinyl alcohol resin containing a component copolymerizable with vinyl acetate. In addition, as polyvinyl alcohol resins, modified polyvinyl alcohol resins containing acetoacetyl groups, sulfonic acid groups, carboxyl groups, aromatic groups, etc., modified polyvinyl alcohol resins having a polyvinyl formal or polyvinyl acetal structure, etc. Can also be used.

  Examples of the modified polyvinyl alcohol-based resin include polymers having at least one side chain of the side chain represented by the following general formula (1) or general formula (2).

In the general formula (1), R ¹ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ² and R ⁶ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched alkoxy group having 1 to 4 carbon atoms, carbon It represents a linear or branched thioalkoxy group of formulas 1 to 4, a halogen, a nitro group, an amino group, a hydroxyl group or a thiol group (however, R ² and R ⁶ are not hydrogen atoms at the same time). R ^{3 to} R ⁵ each independently represent a hydrogen atom or a substituent.

In the general formula (2), R ⁷ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. A ¹ represents a naphthyl group which may have a substituent, an anthranyl group which may have a substituent, or a phenanthrenyl group which may have a substituent. One or more carbon atoms among the carbon atoms constituting the naphthyl group, the anthranyl group, or the phenanthrenyl group may be substituted with a nitrogen atom.

  Moreover, as a modified polyvinyl alcohol-type resin, the polymer which has a repeating unit represented by following General formula (3) can be illustrated.

In the general formula (3), R ⁸ represents a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted phenyl group. R ⁹ , A ² and A ³ are each independently a hydrogen atom, halogen, a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched structure having 1 to 4 carbon atoms. A halogenated alkyl group, a linear or branched alkoxy group having 1 to 4 carbon atoms, an alkoxycarbonyl group, an acyloxy group, an amino group, an azide group, a nitro group, a cyano group, or a hydroxyl group (provided that R ⁹ is not a hydrogen atom).

  Regarding the film containing a polymer having any one of the above general formulas (1) to (3), paragraphs [0060] to [0084] of JP-A-2006-65258 and paragraphs of JP-A-2007-161993 [ [0029] to [0087]. The matters described in the above publication are deemed to have been described in the present specification, and the items to be described are omitted.

<A-2-2. Norbornene resin>
The norbornene-based resin refers to a (co) polymer obtained by using a norbornene-based monomer having a norbornene ring as a part or all of a starting material (monomer). The “(co) polymer” represents a homopolymer or a copolymer (copolymer). The transparent protective film 12 is usually produced by stretching a film containing a norbornene resin formed into a sheet shape.

In the norbornene-based resin, a norbornene-based monomer having a norbornene ring (having a double bond in the norbornane ring) is used as a starting material. The norbornene-based resin may or may not have a norbornane ring in the structural unit in the (co) polymer state. As the norbornene-based resin having a norbornane ring as a structural unit in the state of a (co) polymer, for example, tetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] Dec-3-ene, 8-methyltetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] dec-3-ene, 8-methoxycarbonyltetracyclo [4.4.1 ^2,5 . 1 ^7,10 . 0] Dec-3-ene and the like. A norbornene-based resin having no norbornane ring as a structural unit in the (co) polymer state is, for example, a (co) polymer obtained using a monomer that becomes a 5-membered ring by cleavage. Examples of the monomer that becomes a 5-membered ring by cleavage include norbornene, dicyclopentadiene, 5-phenylnorbornene, and derivatives thereof. When the norbornene-based resin is a copolymer, the arrangement state of the molecules is not particularly limited, and may be a random copolymer, a block copolymer, or a graft copolymer. It may be.

  Examples of the norbornene resin include (a) a polymer obtained by hydrogenating a ring-opening (co) polymer of a norbornene monomer, and (b) a polymer obtained by addition (co) polymerization of a norbornene monomer. (A) A polymer obtained by hydrogenating a ring-opening copolymer of a norbornene monomer is a ring-opening copolymer of one or more norbornene monomers and α-olefins, cycloalkenes and / or non-conjugated dienes. Includes polymers hydrogenated from coalescence. The polymer obtained by addition copolymerization of the above (b) norbornene monomer is a polymer obtained by addition copolymerization of one or more norbornene monomers and α-olefins, cycloalkenes and / or non-conjugated dienes. Include.

  The polymer obtained by hydrogenating the ring-opening (co) polymer of the above (a) norbornene-based monomer is subjected to a metathesis reaction of the norbornene-based monomer or the like to obtain a ring-opening (co) polymer. It can be obtained by hydrogenating the polymer. Specifically, for example, the method described in paragraphs [0059] to [0060] of JP-A-11-116780, the method described in paragraphs [0035] to [0037] of JP-A-2001-350017, and the like. It can be illustrated. The polymer obtained by addition (co) polymerization of the (b) norbornene-based monomer can be obtained, for example, by the method described in Example 1 of JP-A No. 61-292601.

  The norbornene-based resin preferably has a weight average molecular weight (Mw) of 20,000 to 500,000. However, the weight average molecular weight is a value measured by a gel permeation chromatographic method (GPC) method using a tetrahydrofuran solvent. The glass transition temperature (Tg) of the norbornene-based resin is preferably 110 ° C to 180 ° C. However, the glass transition temperature (Tg) is a value determined by a DSC method according to JIS K7121. By setting the weight average molecular weight and the glass transition temperature in the above ranges, a film having good heat resistance and moldability can be obtained.

<A-2-3. Manufacturing method of transparent protective film>
The transparent protective film 12 is obtained by producing (forming) a film from the forming material containing the resin described above by any appropriate molding method, and subjecting the film to stretching treatment as necessary. Examples of the molding method include a compression molding method, a transfer molding method, an injection molding method, an extrusion molding method, a blow molding method, a powder molding method, an FRP molding method, and a solvent casting method. Preferably, the molding method is a solvent casting method or an extrusion molding method. In the solvent casting method, for example, a concentrated solution (dope) in which a forming material containing a resin and other components (additives, etc.) is dissolved in a solvent is degassed and then applied to the surface of an endless stainless steel belt or a rotating drum. It is a method of forming a film by stretching and evaporating the solvent. The extrusion molding method is, for example, a method in which the forming material is heated and melted, extruded onto the surface of a casting roll using a T die or the like, and cooled to form a film. By adopting the above method, the transparent protective film 12 having excellent thickness uniformity can be obtained.

  Any appropriate stretching method can be adopted for the stretching treatment according to the purpose. Examples of the stretching method include a longitudinal uniaxial stretching method, a transverse uniaxial stretching method, a longitudinal and transverse simultaneous biaxial stretching method, and a longitudinal and transverse sequential biaxial stretching method. Examples of the stretching machine that performs this include a roll stretching machine, a tenter stretching machine, and a biaxial stretching machine. Preferably, the stretching machine includes a temperature control unit. When stretching by heating, the internal temperature of the stretching machine may be continuously changed or may be changed stepwise. The stretching direction may be the MD direction or the TD direction. Moreover, you may extend | stretch in the diagonal direction (diagonal extending | stretching) using the extending | stretching method of FIG. 1 of Unexamined-Japanese-Patent No. 2003-262721.

  The temperature for stretching (stretching temperature) is appropriately set according to the type of film. The stretching is preferably carried out in the range of the glass transition temperature (Tg) of the film ± 30 ° C. By stretching under such conditions, a film having a uniform retardation value can be obtained, and crystallization (white turbidity) of the film can be prevented. Specifically, the stretching temperature is preferably 100 ° C to 180 ° C, more preferably 120 ° C to 160 ° C.

  The means for controlling the stretching temperature is not particularly limited, and for example, an air circulation type constant temperature oven in which hot air or cold air circulates, a heater using microwaves or far infrared rays, a roll heated for temperature adjustment, or heated. Examples thereof include a heat pipe roll and a heated metal belt.

  The draw ratio of the film is appropriately set according to the purpose. The draw ratio is preferably more than 1 time and 3 times or less, more preferably more than 1 time and 2.5 times or less, and particularly preferably 1.1 times to 2.0 times. Moreover, the feed rate at the time of stretching is not particularly limited, but is preferably 0.5 m / min to 30 m / min from the viewpoint of mechanical accuracy, stability, and the like.

<A-3. Manufacturing method of polarizing plate>
The polarizing plate 10 having the above-described configuration is obtained by performing the surface modification treatment and the alkali treatment on the surface of the transparent protective film 12 and the surface modification through the polyvinyl alcohol-based adhesive containing the metal compound colloid. It is manufactured by a manufacturing method including a step of bonding the surface of the transparent protective film 12 subjected to the treatment and the alkali treatment to the polarizer 11.
Hereinafter, each of the above steps will be specifically described sequentially.

<A-3-1. Surface modification process>
Any appropriate method can be adopted as the surface modification treatment applied to the surface of the transparent protective film 12. For example, the surface modification treatment may be a dry treatment or a wet treatment. Specific examples of the dry treatment include discharge treatment such as corona discharge treatment and plasma discharge treatment, flame treatment, ozone treatment, UV ozone treatment, ionizing active ray treatment such as ultraviolet treatment and electron beam treatment. In the present invention, among these surface modification treatments, corona discharge treatment, plasma discharge treatment, and UV ozone treatment are preferably used in that continuous treatment is possible and economy and workability are excellent.

As shown in FIG. 2, the corona discharge treatment is performed by applying a high-frequency high voltage between the dielectric roll 20 that conveys the transparent protective film 12 and the electrode 30 that is disposed opposite to the dielectric roll 20. The surface of the film 12 to be transported is modified. By applying a high frequency high voltage between the dielectric roll 20 and the electrode 30, the atmosphere between the dielectric roll 20 and the electrode 30 is dielectrically broken and ionized, and a corona discharge C is generated. By passing the film 12 through the corona discharge C, the surface of the film 12 is modified. The discharge amount (W · min / m ² ) of the corona discharge treatment is defined as E (W) for the electric power (discharge power) applied between the dielectric roll 20 and the electrode 30 and V (m / min), and the length of the electrode 30 is L (m), it is expressed by the following formula (1).
Discharge amount = E / (V × L) (1)
The discharge amount is preferably in a 50~150W · min / ^{m 2,} and more preferably are 60~120W · min / ^{m 2.} The discharge force E, the conveyance speed V of the film 12, and the length L of the electrode 30 are preferably set so that the discharge amount of the corona discharge treatment represented by the above formula (1) is within the above range. .

  In the plasma discharge treatment, the surface of the film 12 is modified by allowing the film 12 to pass through low-temperature plasma generated by glow discharge. When a glow discharge is generated in an atmosphere composed of an inorganic gas such as a low-pressure inert gas, oxygen, or halogen gas, the low-temperature plasma is generated by ionizing a part of gas molecules.

  The UV ozone treatment modifies the surface of the film 12 by irradiating the surface of the film 12 with ultraviolet rays while blowing air containing ozone on the surface of the film 12.

  The atmosphere in which the surface modification treatment described above is performed is not particularly limited, and examples thereof include an air atmosphere, a nitrogen atmosphere, and an argon atmosphere. Further, the atmospheric temperature during the surface modification treatment is preferably 23 to 80 ° C, more preferably 23 to 60 ° C, and further preferably 23 to 50 ° C.

<A-3-2. Alkali treatment process>
The alkali treatment (saponification treatment) applied to the surface of the transparent protective film 12 is performed, for example, by immersing the transparent protective film 12 in an alkaline aqueous solution. By performing the alkali treatment, a hydroxyl group can be introduced on the surface of the transparent protective film 12, and adhesion can be improved in adhesion to the polarizer 11 via an adhesive. The alkali to be used is not particularly limited, and for example, potassium hydroxide or sodium hydroxide is preferably used.

<A-3-3. Bonding process>
In the bonding step, the surface of the transparent protective film 12 that has been subjected to the surface modification treatment and alkali treatment described above and the polarizer 11 are bonded via a polyvinyl alcohol-based adhesive containing a metal compound colloid.

  The polyvinyl alcohol-based adhesive containing a metal compound colloid used in the present invention is a resin solution containing a polyvinyl alcohol-based resin and a metal compound colloid, and further contains a cross-linking agent as necessary. The metal compound colloid preferably has an average particle diameter of 1 nm to 100 nm.

  Examples of the polyvinyl alcohol resin include a polyvinyl alcohol resin and a modified polyvinyl alcohol resin having an acetoacetyl group. Examples of the modified polyvinyl alcohol-based resin having an acetoacetyl group include, for example, “GOHSENOL Z series” manufactured by Nippon Synthetic Chemical Co., Ltd., “GOHSENOL NH series” manufactured by the company, and “GO For example, “Cefaimer Z Series”.

  Examples of the polyvinyl alcohol resin include a saponified product of polyvinyl acetate and a derivative thereof; a saponified product of a copolymer of vinyl acetate and a monomer copolymerizable therewith; acetalization, urethanization, ether of polyvinyl alcohol Examples thereof include modified polyvinyl alcohols that have been modified, grafted, phosphoric esterified, and the like. Examples of the copolymerizable monomer include unsaturated carboxylic acids such as maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, acrylic acid, methacrylic acid, and esters thereof; ethylene, propylene, and the like. Α-olefin containing: allyl sulfonic acid, methallyl sulfonic acid, sodium allyl sulfonate, sodium methallyl sulfonate, sodium sulfonate, sodium sulfonate monoalkylmalate, sodium alkylsulfonate maleate, alkali salt of acrylamide alkyl sulfonate Examples thereof include sulfonic acid group-containing monomers such as N-methylolacrylamide; N-vinylpyrrolidone and derivatives thereof.

  The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 5000, more preferably 1000 to 4000, from the viewpoint of adhesiveness. The average degree of saponification of the polyvinyl alcohol-based resin is preferably 85 to 100 mol%, more preferably 90 to 100 mol%, from the viewpoint of adhesiveness.

  The modified polyvinyl alcohol-based resin having an acetoacetyl group can be obtained, for example, by reacting a polyvinyl alcohol-based resin and diketene by an arbitrary method. Specifically, for example, (a) a method of adding diketene to a dispersion in which a polyvinyl alcohol resin is dispersed in a solvent such as acetic acid, and (b) a polyvinyl alcohol resin in a solvent such as dimethylformamide or dioxane. Examples thereof include a method of adding diketene to the dissolved solution, and (c) a method of directly contacting a diketene gas or liquid diketene with a polyvinyl alcohol resin.

  The degree of acetoacetyl group modification of the modified polyvinyl alcohol resin having an acetoacetyl group is, for example, 0.1 mol% or more. By using a modified polyvinyl alcohol resin having an acetoacetyl group modification degree within the above range, an adhesive having better water resistance can be obtained. The degree of acetoacetyl group modification is preferably 0.1 to 40 mol%, more preferably 1 to 20 mol%, and even more preferably 2 to 7 mol%. The degree of acetoacetyl modification is a value measured by, for example, a nuclear magnetic resonance (NMR) method.

  Arbitrary appropriate crosslinking agents are employable as said crosslinking agent. The cross-linking agent is preferably a compound having at least two functional groups having reactivity with the polyvinyl alcohol resin. Examples of the crosslinking agent include alkylene diamines having two alkylene groups and amino groups such as ethylene diamine, triethylene diamine, and hexamethylene diamine; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, tolyl. Phenylmethane triisocyanate, methylenebis (4-phenyl) methane triisocyanate, isophorone diisocyanate, and isocyanates such as ketoxime block product or phenol block product; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether Glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimer Epoxys such as roll propane triglycidyl ether, diglycidyl aniline, diglycidyl amine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde; glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleindialdehyde Dialdehydes such as phthaldialdehyde; aminoformaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, and condensates of benzoguanamine and formaldehyde; sodium, potassium, magnesium, calcium And salts of metals such as aluminum, iron and nickel, and oxides thereof. Of these, aminoformaldehyde resins and dialdehydes are preferred. The amino formaldehyde resin is preferably a compound having a methylol group. Glyoxal is preferred as the dialdehyde. Among them, a compound having a methylol group is preferable, and methylol melamine is particularly preferable. Examples of the aldehyde compound include a product name “Glyoxal” manufactured by Nippon Synthetic Chemical Co., Ltd., a product name “Sequaretz 755” manufactured by OMNOVA, and the like. Examples of the methylol compound include trade name “Watersol Series” manufactured by Dainippon Ink Co., Ltd.

  The blending ratio of the crosslinking agent is, for example, 1 to 60 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol resin (preferably a modified polyvinyl alcohol resin having an acetoacetyl group). An adhesive having a crosslinking agent content in the above range can form an adhesive layer excellent in transparency, adhesiveness, and water resistance. The upper limit of the blending ratio of the crosslinking agent is preferably 50 parts by mass, more preferably 30 parts by mass, still more preferably 15 parts by mass, particularly preferably 10 parts by mass, and most preferably 7 parts by mass. Part. The lower limit of the blending amount is preferably 5 parts by mass, more preferably 10 parts by mass, and even more preferably 20 parts by mass. In addition, since the polyvinyl alcohol-type adhesive of this invention contains the metal compound colloid, even if it is a case where many crosslinking agents are mix | blended, it is excellent in stability.

  The metal compound colloid may be, for example, one in which fine particles are dispersed in a dispersion medium, or one that is electrostatically stabilized due to mutual repulsion of the same kind of fine particles and has permanent stability. Good. The average particle diameter of the metal compound fine particles (colloid) is not particularly limited, but is preferably 1 nm to 100 nm, and more preferably 1 nm to 50 nm. Since the metal compound colloid having such an average particle size can be dispersed substantially uniformly in the dispersion medium, the adhesive containing the colloid is excellent in adhesiveness, and the transparent protective film 12 and the polarizer 11 Generation of nicks at the interface can be suppressed.

  Any appropriate compound can be adopted as the metal compound. Examples of the metal compound include metal oxides such as alumina, silica, zirconia, and titania; metal salts such as aluminum silicate, calcium carbonate, magnesium silicate, zinc carbonate, barium carbonate, and calcium phosphate; celite, talc, clay, Examples include minerals such as kaolin. The metal compound is preferably alumina.

  The metal compound colloid is present, for example, in a colloid solution in which the metal compound is dispersed in a dispersion medium. Examples of the dispersion medium include water and alcohols. The solid content concentration in the colloidal solution is, for example, 1 to 50% by mass. The colloidal solution may contain an acid (for example, nitric acid, hydrochloric acid, acetic acid, etc.) as a stabilizer.

  Metal compound colloids are electrostatically stable and can be divided into colloids having a positive charge and colloids having a negative charge. Positive charge and negative charge are distinguished by the charge state of the colloidal surface charge in the colloidal solution. The charge of the metal compound colloid can be confirmed, for example, by measuring the zeta potential. The surface charge of a metal compound colloid generally varies with pH. Therefore, the charge of the colloidal solution is affected by the pH of the prepared adhesive (resin solution). The pH of the adhesive is usually 2 to 6, preferably 2.5 to 5, more preferably 3 to 5, and further preferably 3.5 to 4.5. In the present invention, the adhesive containing a metal compound colloid having a positive charge can suppress the occurrence of nicks more than the adhesive containing a metal compound colloid having a negative charge. Examples of the positively charged metal compound colloid include alumina colloid and titania colloid, and alumina colloid is particularly preferable.

  The blending ratio (in terms of solid content) of the metal compound colloid is preferably 200 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol resin. The adhesive having the above blending ratio can more appropriately suppress the occurrence of nicks while ensuring adhesiveness. The blending ratio of the metal distribution compound colloid is more preferably 10 to 200 parts by mass, still more preferably 20 to 175 parts by mass, and particularly preferably 30 to 150 parts by mass.

  The viscosity of the polyvinyl alcohol-based adhesive (resin solution) containing the metal colloid is not particularly limited, but is preferably 1 to 50 mPa · s. In general, the occurrence of nicks increases as the viscosity of the adhesive decreases. However, the polyvinyl alcohol adhesive of the present invention can suppress the occurrence of nicks even with a relatively low viscosity as described above.

  The polyvinyl alcohol-based adhesive is prepared by mixing a polyvinyl alcohol-based resin and a cross-linking agent in a dispersion medium and blending a metal compound therein. Further, in the polyvinyl alcohol adhesive, there are coupling agents such as silane coupling agents and titanium coupling agents, tackifiers, UV absorbers, antioxidants, heat stabilizers, hydrolysis stabilizers, and the like. It may be included. Although the metal compound colloid of the present invention is a non-conductive material, the colloid may contain fine particles of a conductive substance.

  The application of the polyvinyl alcohol-based adhesive containing the metal compound colloid may be performed on any adhesive surface of the polarizer 11 or the transparent protective film 12, or on both adhesive surfaces of the polarizer 11 and the transparent protective film 12. You may go. The adhesive is applied so as to have a dry thickness of 10 nm to 300 nm, preferably 10 nm to 200 nm, and more preferably 20 nm to 150 nm.

<B. Liquid crystal display>
FIG. 3 is a longitudinal sectional view schematically showing a configuration example of a liquid crystal panel included in the liquid crystal display device according to the embodiment of the present invention. The liquid crystal panel 100 includes a liquid crystal cell 40, a polarizing plate 10A disposed on the viewing side of the liquid crystal cell 40, and a polarizing plate 10B disposed on the opposite side of the viewing side of the liquid crystal cell 40. The polarizing plate 10 according to the present invention described above with reference to FIG. 1 is used as at least one of the polarizing plates 10A and 10B. Preferably, the polarizing plate 10 according to the present invention is used for both of the polarizing plates 10A and 10B. The polarizing plate 10A and the polarizing plate 10B are disposed in the liquid crystal cell 40 so that the absorption axis directions of the polarizers 11 are orthogonal to each other. The liquid crystal panel 100 may be provided with an arbitrary birefringent layer or an optical film between the polarizing plate 10 </ b> A and the liquid crystal cell 40 and / or between the polarizing plate 10 </ b> B and the liquid crystal cell 40. Further, the members constituting the liquid crystal panel 100 are bonded via an arbitrary adhesive layer.

  Examples of the liquid crystal cell 100 include an active matrix type liquid crystal cell using a thin film transistor. The liquid crystal cell 100 may be a simple matrix type liquid crystal cell as used in a super twist nematic liquid crystal display device.

  The liquid crystal cell 100 generally includes a pair of substrates and a liquid crystal layer as a display medium sandwiched between the pair of substrates. Specifically, a space is formed by arranging a spacer between the pair of substrates, and a liquid crystal layer in which liquid crystal molecules are sealed is formed in this space. Of the pair of substrates, one substrate (active matrix substrate) includes, for example, a switching element (for example, TFT) for controlling the electro-optical characteristics of the liquid crystal, and a scanning line and a source signal for supplying a gate signal to the switching element. Is provided. Of the pair of substrates, the other substrate (color filter substrate) is provided with a color filter, for example. The color filter may be provided on the active matrix substrate. However, when RGB three-color light sources are used as the illumination means of the liquid crystal display device as in the field sequential method, the color filter can be omitted.

  As the liquid crystal cell 100 used in the liquid crystal display device according to the present invention, according to the drive mode classification, for example, twisted nematic (TN) mode, super twisted nematic (STN) mode, horizontal alignment (ECB) mode, vertical Various liquid crystal cells such as alignment (VA) mode, in-plane switching (IPS) mode, bend nematic (OCB) mode, ferroelectric liquid crystal (SSFLC) mode, and antiferroelectric liquid crystal (AFLC) mode can be exemplified.

  The twisted nematic (TN) mode liquid crystal cell is a liquid crystal cell in which a nematic liquid crystal having positive dielectric anisotropy is sandwiched between a pair of substrates, and the liquid crystal molecular alignment is twisted 90 degrees by the surface alignment treatment of the glass substrate. I say something. Specific examples include the liquid crystal cell described in “Bakufukan Co., Ltd.,” “Liquid Crystal Dictionary”, page 158 (1989), and the liquid crystal cell described in JP-A-63-279229.

  The vertical alignment (VA) mode liquid crystal cell uses a voltage controlled birefringence (ECB) effect, and nematic liquid crystal having a negative dielectric anisotropy between transparent electrodes is vertical when no voltage is applied. An aligned liquid crystal cell. Specifically, liquid crystal cells described in JP-A-62-210423 and JP-A-4-153621 can be exemplified. Further, as described in JP-A-11-258605, the VA mode liquid crystal cell has a structure in which a slit is provided in a pixel or a projection is formed on the surface in order to enlarge a viewing angle. A multi-domain MVA mode liquid crystal cell may be used by using a material. Further, as described in Japanese Patent Application Laid-Open No. 10-123576, a VATN mode in which a chiral agent is added to a liquid crystal, the liquid crystal is substantially vertically aligned when no nematic liquid crystal voltage is applied, and twisted multi-domain alignment is applied when a voltage is applied. A liquid crystal cell may be used.

  The in-plane switching (IPS) mode liquid crystal cell is a so-called sandwich cell in which a liquid crystal is sealed between a pair of parallel substrates by using an electrically controlled birefringence (ECB) effect. In this state, nematic liquid crystal that is homogeneously aligned in a non-conductive state is made to respond with an electric field parallel to the substrate (also referred to as a transverse electric field). Specifically, Techno Times publication “Monthly Display July issue”, pages 83-88 (1997 version) and Japanese Liquid Crystal Society publication “Liquid Crystal vol.2 No.4”, pages 303-316 (1998 version). As described, when the major axis of the liquid crystal molecules and the polarization axis of the incident-side polarizing plate are aligned and the upper and lower polarizing plates are arranged perpendicularly, the display becomes completely black without an electric field, In a certain state, the liquid crystal molecules can obtain transmittance according to the rotation angle by rotating while maintaining a state parallel to the substrate.

  The liquid crystal cell of the above-mentioned bend nematic (OCB: Optically Compensated Bend or Optically Compensated Birefringnence) mode uses a voltage controlled birefringence (ECB) effect, and nematic with positive dielectric anisotropy between transparent electrodes. This means a bend-aligned liquid crystal cell in which twisted alignment exists in the center when no voltage is applied. The OCB mode liquid crystal cell is also referred to as a “π cell”. Specifically, those described in Kyoritsu Publishing Co., Ltd. “Next Generation Liquid Crystal Display” (2000), pages 11 to 27 and those described in JP-A-7-084254 can be exemplified.

  The liquid crystal display device according to the present invention includes the liquid crystal panel 100 described above. The liquid crystal display device according to the present invention may have the same configuration as the conventional liquid crystal display device except that the liquid crystal panel 100 is included. For example, the liquid crystal display device according to the present invention includes at least the liquid crystal panel 100 and a backlight unit disposed on one side of the liquid crystal panel 100. The backlight unit may be a direct type or a side light type.

  When the direct system is adopted, the backlight unit preferably includes at least a light source, a reflection film, a diffusion plate, a prism sheet, and a brightness enhancement film. When the sidelight method is adopted, the backlight unit preferably includes at least a light source, a reflection film, a diffusion plate, a prism sheet, a brightness enhancement film, a light guide plate, and a light reflector. Note that some of these members may be omitted or replaced with other members depending on the illumination method of the liquid crystal display device, the driving mode of the liquid crystal cell, and the like.

  The liquid crystal display device according to the present invention may be a transmissive type in which the screen is viewed by irradiating light from the opposite side of the liquid crystal panel 100, or the screen is viewed by irradiating light from the viewing side of the liquid crystal panel. A reflective type may also be used. Alternatively, the liquid crystal display device according to the present invention may be a transflective type having both transmissive and reflective properties.

  Applications of the liquid crystal display device according to the present invention include, for example, OA equipment such as a personal computer monitor, notebook personal computer, and copy machine, mobile equipment such as a mobile phone, a clock, a digital camera, a personal digital assistant (PDA), and a portable game machine, Household electrical equipment such as video cameras, TVs, microwave ovens, back monitors, car navigation system monitors, car audio equipments, display equipment such as commercial store information monitors, security equipment such as surveillance monitors, Or, nursing care / medical devices such as nursing care monitors and medical monitors can be exemplified.

  A preferred application of the liquid crystal display device according to the present invention is a television. The screen size of the television is preferably a wide 17 type (373 mm × 224 mm) or more, more preferably a wide 23 type (499 mm × 300 mm) or more, and further preferably a wide 32 type (687 mm × 412 mm). That's it.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

<A. Measuring method of various parameters>
The measurement method of various parameters in the present examples and comparative examples is as follows.
(1) Measuring method of nx, ny, nz, Re [590] and Nz coefficient:
It measured at 23 degreeC using the product name "KOBRA21-ADH" by Oji Scientific Instruments. In addition, the value measured using the Abbe refractometer (The product made from Atago Co., Ltd. product name "DR-M4") was used for the average refractive index. Here, “nx” means the refractive index in the direction in which the in-plane refractive index of the film is maximum (that is, the slow axis direction), and “ny” is perpendicular to the slow axis in the plane of the film. Means a refractive index in a certain direction (that is, a fast axis direction). “Nz” means the refractive index in the thickness direction of the film. “In-plane retardation value (Re [λ])” means an in-plane retardation value measured with light having a wavelength λ (nm) at 23 ° C. Re [λ] can be obtained by Re [λ] = (nx−ny) × d, where d (nm) is the thickness of the film. “Thickness direction retardation value (Rth [λ])” means a retardation value in the thickness direction of the film measured with light having a wavelength λ (nm) at 23 ° C. Rth [λ] can be obtained by Rth [λ] = (nx−nz) × d, where d (nm) is the thickness of the film. The “Nz coefficient” is a value calculated from the above Rth [λ] / Re [λ]. In the present invention, it is a value calculated from Rth [590] / Re [590] when λ = 590 nm. is there.

(2) Measuring method of thickness:
When the thickness was less than 10 μm, the measurement was performed using a spectrophotometer for thin film (product name “instant multiphotometry system MCPD-2000”) manufactured by Otsuka Electronics Co., Ltd. When the thickness was 10 μm or more, measurement was performed using a digital micrometer (“KC-351C type”) manufactured by Anritsu Corporation.

(3) Measurement of adhesive viscosity:
It measured using the rheometer (the product made by HAAKE, RSI-HS).
(4) Measurement of average particle size of colloid:
It measured using the particle size distribution meter (the Nikkiso Co., Ltd. make, Nanotrac UPA150).
(5) Measurement of surface roughness (Ra) of transparent protective film:
Measurement was performed using NanoScope IV manufactured by Veeco.
(6) Measurement of element ratio on transparent protective film surface:
Measurement was performed using Quantera SXM manufactured by ULVAC-PHI.

<B. Example 1>
[B-1. Production of polarizer]
A polymer film (trade name “VF-PS # 7500” manufactured by Kuraray Co., Ltd.) mainly composed of a polyvinyl alcohol resin having a thickness of 75 μm is placed in five baths under the following conditions (1) to (5). The film was sequentially immersed while applying tension in the longitudinal direction of the film, and stretched so that the final stretching ratio (cumulative stretching ratio) was 6.2 times the original length of the film. The stretched film thus obtained was dried in an air circulation oven at 40 ° C. for 1 minute to produce a polarizer.
(1) Swelling bath: 30 ° C pure water (2) Dyeing bath: 30 ° C aqueous solution containing 0.032 parts by weight iodine and 0.2 parts by weight potassium iodide with respect to 100 parts by weight water. 3) First crosslinking bath: 40 ° C. aqueous solution containing 3 wt% potassium iodide and 3 wt% boric acid (4) Second crosslinking bath: 5 wt% potassium iodide, 4 60 ° C. aqueous solution containing 5% by weight boric acid (5) Washing bath: 25 ° C. aqueous solution containing 3% by weight potassium iodide

[B-2. Preparation of adhesive]
Modified polyvinyl alcohol-based resin having an acetoacetyl group (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “Gosefimer Z200”, average polymerization degree: 1200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) 100 parts by mass and 50 parts by mass of methylolmelamine were dissolved in pure water under a temperature condition of 30 ° C. to obtain an aqueous solution having a solid content concentration of 3.7% by mass. To 100 parts by mass of this aqueous solution, 18 parts by mass of an alumina colloid aqueous solution (average particle size: 15 nm, solid content concentration: 10%, positive charge) was added. The obtained solution (polyvinyl alcohol-based adhesive containing a metal compound colloid) was used as an adhesive for laminating the polarizer and the transparent protective film. The adhesive had a viscosity of 9.6 mPa · s and a pH of 4 to 4.5.

[B-3. Corona discharge treatment and alkali treatment of transparent protective film]
As a transparent protective film, a stretched Arton film (manufactured by JSR) formed from a norbornene-based resin was used, and the surface was subjected to corona discharge treatment under the following conditions (1) to (5).
(1) Discharge amount: 116 W · min / m ²
(2) Discharge power: 0.15 kW
(3) Film transport speed: 3 m / min
(4) Length of electrode: 0.43m
(5) Distance between film and electrode: 2 mm

  Next, an alkali treatment was performed by immersing the film subjected to the corona discharge treatment in an aqueous sodium hydroxide solution (40 ° C., pH 13) for 30 seconds.

[B-4. Preparation of polarizing plate]
The above adhesive was applied on both surfaces of the above polarizer with a rod coater so that the thickness after drying was 0.05 μm. And said Arton film was laminated | stacked on one side of the polarizer. At this time, the arton film was laminated so that the surface subjected to corona discharge was opposed to the adhesive. On the other hand, on the other surface of the polarizer, a commercially available triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd., trade name “Fujitac UZ”) was laminated after alkali treatment in the same manner as the above Arton film. This laminate was dried for 5 minutes in an air-circulating constant temperature oven at 110 ± 1 ° C. to produce a polarizing plate, where the angle formed between the absorption axis of the polarizer and the slow axis of the ARTON film was substantially perpendicular. (90 ° ± 0.5 °).

<C. Example 2>
[C-1. Production of transparent protective film]
A modified polyvinyl alcohol-based resin (polymer represented by the formula (XI) in the same publication) described in Example 3 of [0103] to [0106] of JP-A-2007-161993 was prepared. This resin was dissolved in dichloromethane, and the solution was cast on a polyethylene terephthalate film substrate (thickness 70 μm) and dried to form a 110 μm thick resin film. After peeling this resin film from the base material, it was stretched free end in the width direction at 140 ° C. twice. The resin film after stretching had a thickness of 50 μm. Further, the refractive index ellipsoid of the stretched resin film was nx> ny = nz (Nz = 1.00), and Re [590] was 140 nm.

[C-2. Preparation of polarizing plate]
A polarizing plate was produced under the same conditions and method as in Example 1 except that the stretched resin film was used instead of the Arton film of Example 1 as one transparent protective film of the polarizing plate.

<D. Example 3>
A polarizing plate was produced under the same conditions and method as in Example 1 except that the discharge power of the corona discharge treatment applied to the transparent protective film was 0.05 kW (discharge amount = 38 W · min / m ² ).

<E. Comparative Example 1>
A polarizing plate was produced under the same conditions and method as in Example 1 except that the Arton film was not subjected to alkali treatment.

<F. Comparative Example 2>
A polarizing plate was produced under the same conditions and method as in Example 1 except that the Arton film was not subjected to corona discharge treatment.

<G. Comparative Example 3>
[G-1. Preparation of adhesive]
An adhesive was produced under the same conditions and method as in Example 1 except that the aqueous alumina colloid solution was not added.

[G-2. Preparation of polarizing plate]
As an adhesive for laminating a polarizer and a transparent protective film, a polarizing plate was used under the same conditions and method as in Example 1 except that the above-mentioned adhesive was used instead of the adhesive in Example 1. Produced.

<H. Evaluation>
[H-1. Evaluation of surface roughness (Ra)]
Before the surface roughness (Ra) of the transparent protective film (Arton film) of Example 1 and the transparent protective film (modified polyvinyl alcohol-based resin film) of Example 2 is subjected to corona discharge treatment and alkali treatment (untreated), After performing only corona discharge treatment, after performing only alkali treatment, it measured about each after performing both corona discharge treatment and alkali treatment. Table 1 shows the measurement results.

  As shown in Table 1, the surface of the transparent protective film is roughened by performing both corona discharge treatment and alkali treatment, and this contributes to the improved adhesion between the polarizer and the transparent protective film. Conceivable.

[H-2. Evaluation of element ratio]
The element ratio of the surface of the transparent protective film (Arton film) of Example 1 was subjected to corona discharge treatment and alkali treatment (untreated), after corona discharge treatment only, after only alkali treatment, and then corona discharge. It measured about each after giving both a process and an alkali treatment. Table 2 shows the measurement results. In addition, the numerical value in Table 2 means atomic%.

  As shown in Table 2, by performing corona discharge treatment and alkali treatment, there are functional groups active in adhesion such as N, O, and Na. This contributes to adhesion between the polarizer and the transparent protective film. It is thought that the property improved.

[H-3. Evaluation of durability (adhesiveness) of polarizing plate]
About the polarizing plate of Examples 1-3 and Comparative Examples 1-3, the evaluation test of following (1)-(4) was done.

(1) Initial peeling test The polarizing plate cut out to size 25 mm x 50 mm was affixed on the slide glass using the acrylic adhesive. At this time, the Arton film side for the polarizing plates of Examples 1 and 3 and Comparative Examples 1 to 3 and the modified polyvinyl alcohol-based resin film side for the polarizing plate of Example 2 were attached to the slide glass, respectively. Then, a cutter blade is inserted between the polarizer and the ARTON film, or between the polarizer and the modified polyvinyl alcohol resin film, and whether or not the polarizer and each film can be peeled off is bonded to each other. Sex was evaluated.

(2) 60 ° C. hot water test A polarizing plate cut out into a size of 25 mm × 50 mm was immersed in a constant temperature water bath at 60 ± 1 ° C. for 5 hours, taken out, dried naturally at room temperature, and a polarizer and a transparent protective film (Example 1 3 and the polarizing plates of Comparative Examples 1 to 3 were visually observed for the peeling state between the Arton film and the polarizing plate of Example 2 with the modified polyvinyl alcohol resin film.

(3) 60 ° C. and 90% RH test A polarizing plate cut out to a size of 25 mm × 50 mm is taken out after being left in an environmental tester of 60 ± 1 ° C. and 90 ± 5% RH for 200 hours, allowed to cool naturally to room temperature, and polarized. The peeled state between the substrate and the transparent protective film (Arton film for the polarizing plates of Examples 1 and 3 and Comparative Examples 1 to 3 and modified polyvinyl alcohol resin film for the polarizing plate of Example 2) was visually observed. .

(4) Heating test at 80 ° C. A polarizing plate cut out in a size of 25 mm × 50 mm is left after being left in an air-circulating constant temperature oven at 80 ± 1 ° C. for 200 hours, and then naturally cooled to room temperature, and a polarizer and a transparent protective film ( For the polarizing plates of Examples 1 and 3 and Comparative Examples 1 to 3, the peeled state between the Arton film and the polarizing plate of Example 2 with the modified polyvinyl alcohol resin film was visually observed.

Table 3 shows the results of the evaluation tests (1) to (4).

As shown in Table 3, unlike the polarizing plates of Comparative Examples 1 to 3, the polarizing plates of Examples 1 to 3 peel off at the interface between the polarizer and the transparent protective film even under humidification and heating conditions. It is hard to occur and it can be seen that the adhesiveness is improved. In particular, the adhesive properties of the polarizing plates of Examples 1 and ^{2 in} which the discharge amount of the corona discharge treatment was 50 to 150 W / min / m ² were significantly improved.

[H-4. Evaluation of occurrence of nicks]
About the polarizing plate of Examples 1-3 and Comparative Examples 1-3, the presence or absence of the occurrence of a nick was evaluated by the following conditions and methods.

  The liquid crystal panel was taken out from a commercially available liquid crystal television (manufactured by BanQ, 32-inch liquid crystal television, trade name “DV3250”). The liquid crystal cell was taken out from the liquid crystal panel by neatly removing the optical member disposed on the viewing side and the side opposite to the viewing side of the liquid crystal panel.

  A commercially available polarizing plate (manufactured by Nitto Denko Corporation, trade name “NIBCOM-NXP”) is pasted on the opposite side (backlight side) of the liquid crystal cell via an acrylic adhesive having a thickness of 12 μm. It was. The commercially available polarizing plate includes a triacetyl cellulose film having a thickness of 80 μm, a polarizer, a triacetyl cellulose film having a thickness of 80 μm, and a polyimide resin film having a thickness of 4 μm (Re [590] = 55 nm, Rth [590]. = 240 nm).

  The polarizing plates of Examples 1 to 3 and Comparative Examples 1 to 3 were bonded to the viewing side of the liquid crystal cell via an acrylic pressure-sensitive adhesive having a thickness of 12 μm to prepare test liquid crystal panels. Each test liquid crystal panel was displayed in black after 30 minutes had passed since the backlight was lit in a dark room at 23 ° C. The black display screen was visually observed, and the number of spots (knics) where light was lost in the center of the screen was counted.

  As a result of the above test, the polarizing plate of Comparative Example 3 in which the alumina colloid aqueous solution was not added to the adhesive had many nicked portions and had practical problems. In contrast, in the polarizing plates of Examples 1 to 3, generation of nicks could not be confirmed. That is, according to this invention, it turned out that generation | occurrence | production of the nick in the interface of a polarizer and a transparent protective film can be suppressed.

FIG. 1 is a longitudinal sectional view schematically showing a configuration of a polarizing plate according to one embodiment of the present invention. 2A and 2B are explanatory views for explaining the corona discharge treatment, in which FIG. 2A shows a plan view and FIG. 2B shows a front view. FIG. 3 is a longitudinal sectional view schematically showing a configuration example of a liquid crystal panel included in the liquid crystal display device according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10A, 10B ... Polarizing plate 11 ... Polarizer 12 ... Transparent protective film 20 ... Dielectric roll 30 ... Electrode 40 ... Liquid crystal cell 100 ... Liquid crystal panel

Claims (7)

A step of subjecting the surface of the transparent protective film to surface modification treatment and alkali treatment;
And a step of bonding the surface of the transparent protective film subjected to the surface modification treatment and the alkali treatment to a polarizer via a polyvinyl alcohol-based adhesive containing a metal compound colloid. Manufacturing method.   The method for producing a polarizing plate according to claim 1, wherein the surface modification treatment is at least one of a corona discharge treatment, a plasma discharge treatment, and a UV ozone treatment. The method for producing a polarizing plate according to claim 2, wherein the surface modification treatment is a corona discharge treatment with a discharge amount of 50 to 150 W · min / m ² .   The polarized light according to any one of claims 1 to 3, wherein the transparent protective film is formed of any one of polyvinyl alcohol resin, norbornene resin, acrylic resin, and polyester resin. A manufacturing method of a board.   The method for producing a polarizing plate according to claim 1, wherein the metal compound colloid is an alumina colloid.   A polarizing plate obtained by the production method according to claim 1.   A liquid crystal display device comprising the polarizing plate according to claim 6.

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